A wide number of pathological conditions are characterized by the need to suppress gastric acid secretion. Such conditions include, but are not limited to Zollinger/Ellison syndrome (ZES), gastroesophageal reflux disease (GERD), peptic ulcer disease, duodenal ulcers, esophagitis, and the like. Conditions such as peptic ulcers can have serious complications and represent some of the most prevalent diseases in industrialized nations.
Presently, the main therapies employed in the treatment of GERD and peptic ulcer diseases include agents for reducing the stomach acidity, for example by using the histamine H2-receptor antagonists or proton pump inhibitors (PPIs). PPIs act by inhibiting the parietal cell H+/K+ ATPase proton pumps responsible for acid secretion from these cells. PPIs, such as omeprazole, and its pharmaceutically acceptable salts are disclosed for example in EP 05129, EP 124495 and U.S. Pat. No. 4,255,431.
PPI agents are acid-labile pro-drugs that are usually administered in enteric-coated granules and are weak bases. Following absorption in the small intestine, PPIs preferentially accumulate within the acid milieu of the acid-secreting parietal cells. The acid environment within the acid milieu of parietal cells causes the conversion of the pro-drugs into the active sulfenamides, which are the active agents that bind and inhibit the parietal cell H+/K+ ATPase pumps. Thus, pre-activation of parietal cells is required for the conversion of PPIs to its active protonated form. The pre-activation of parietal cells is usually achieved by meal ingestion that initiates gastrin-dependent parietal cell activation. Indeed, patients are instructed to take PPI one hour prior to meal intake in order to ensure that parietal cells are activated when the PPI reaches the parietal cells via blood stream.
Despite their well-documented efficacy, PPIs have notable limitations. The conversion of PPI to its active form requires pre-activation of parietal cells. The pre-activation of parietal cells is normally achieved by ingestion of food. Thus, the PPI must be taken prior to ingestion of food in order to synchronize between the pre-activation of parietal cells and PPI absorption in blood. Furthermore, PPIs have a relatively slow onset of pharmacological action and may require several days to achieve maximum acid suppression and symptom relief, limiting their usefulness in on-demand GERD therapy (Sachs G, Eur J Gastroenterol Hepatol. 2001; 13 Suppl 1:S35-41).
Moreover, PPIs fail to provide 24-h suppression of gastric acid and nocturnal acid breakthrough that leads to heartburn pain in GERD patients and occurs even with twice-daily dosing of PPIs (Tytgat G N, Eur J Gastroenterol Hepatol. 2001; 13 Suppl 1:S29-33; Shaker R. et al., Am. J. of Gastroenterology, 98 (7), 2003). Finally, these drugs exhibit substantial inter-patient variability in pharmacokinetics and may have significant interactions with other drugs (Hatlebakk et al., Clin Pharmacokinet. 1996; 31(5):386-406). Thus, an improvement of PPI-mediated activity is a well-recognized challenge in gastroenterology.
Maleic acid and succinic acid, chemically characterized as four-carbon dicarboxylic acids, are known as powerful stimulants of gastric acid secretion (Teyssen et al., J. Clin Invest. 1999 103(5): 707-713). Teyssen et al. studied the stimulation of gastric acid secretion in fermented alcoholic beverages produced by fermentation (e.g., beer and wine). Interestingly, maleic acid and succinic acid were found to stimulate gastric acid output in humans as that produced by beer, champagne, wine, and pentagastrin (a powerful exogenous stimulus to induce acid secretion), but without gastrin being their mediator of action.
U.S. Pat. No. 5,559,152 discloses that a mixture of succinic acid and citric acid in the dose of 3.5 mg/kg is capable of inducing gastric acid secretion in dogs as reflected by significant reduction in the pH of the gastric juice measured on an empty stomach 40 min following drug administration. This patent further discloses that succinic and citric acid stimulate acid secretion in healthy human volunteers.
Pokrovskiy et al. (Physiologicheskiy Z'urnal 10:1567-1573, 1973) also disclosed that molecules involved in the mitochondrial respiration circle (krebs cycle) such as pyruvate, succinate, alpha-ketoglutarate, malate or glucose may stimulates proton secretion in ex vivo model of frog mucosa.
U.S. Pat. Nos. 6,489,346; 6,645,988; and 6,699,885; to Phillips (jointly the “Phillips patents”) disclose pharmaceutical compositions and methods of treating acid-caused gastrointestinal disorders using oral compositions consisting of a PPI, at least one buffering agent and specific parietal cell activators. The parietal cell activators disclosed in the Phillips patents include, for example, chocolate, sodium bicarbonate, calcium, peppermint oil, spearmint oil, coffee, tea and colas, caffeine, theophylline, theobromine and amino acids residues. As indicated in the Phillips patents, all these proposed parietal cell activators induce the release of endogenous gastrin leading to stimulatory effects on acid secretion.
All parietal cell activators taught by the prior art to facilitate PPI activity are either gastrin analogs or parietal cell activators that induce release of endogenous gastrin. Applicants surprisingly discovered compositions and methods of effectively facilitating the inhibitory activity of PPIs in a gastrin-independent manner, without activating the gastrin-histamine pathway. The prior art fails to teach or suggest a gastrin-independent manner of facilitating the inhibitory effect of PPIs.
The development of an effective gastrin-independent treatment for pathologies in which inhibition of gastric acid secretion is required would fulfill a long felt need. Despite the wide-spread use of PPIs, a need still exist for increasing the PPI efficacy, e.g., prolonged effect to control night time acid breakthrough, greater effect at reduced dosage and meal-independent administration. Applicants' invention disclosed herein meets many of these long felt needs.